This invention relates to application of coatings and, more particularly, to a roller coating apparatus for applying an adhesive coating to a work piece.
Stacked steel sheets (e.g., discs) are used in electric motors and generators to support magnetic windings and insulation. In operation, an electric current through the magnetic windings produces a magnetic field to actuate a rotor. The magnetic field passes at least partially through the stacked steel sheets that are secured together by welding or an adhesive. Disadvantageously, welded stacked steel sheets may short out the magnetic windings and current methods of applying the adhesive to the steel sheets may result in inconsistent adhesive thicknesses. Variation in adhesive thickness may result in residual stress on the stacked sheets which in turn may lead to magnetic field loss when the magnetic field passes through the stacked steel sheets.
Coating machines are used to apply a coating of the adhesive to a surface of each steel sheet before stacking the sheets together. A coating machine includes a conveyor that moves a steel sheet that is to be coated into contact with a rolling surface of a rotating applicator roll. Before contacting the steel sheet, the rolling surface picks up a coating material from a wetting container as the applicator roll rotates. A doctor blade then scrapes the rolling surface to remove excess coating material and control a coating material thickness before the applicator roll transfers the coating material to the steel sheet.
Disadvantageously, the removed excess coating material often overflows from the doctor blade, is difficult to contain and clean-up, and the scraping force of the doctor blade against the applicator roll often wears out the doctor blade in relatively short periods of time. The wear on the doctor blade may result in inconsistent coating material thickness that may ultimately lead to residual stress in the steel sheets.
Accordingly, a coating apparatus that applies material of consistent thickness while minimizing blade wear is desired. This invention addresses those needs and provides enhanced capabilities while avoiding the shortcomings and drawbacks of the prior art.